The present invention relates to an inkjet head for an inkjet printing apparatus, and more particularly to a structure of an inkjet head.
Recently, inkjet printing apparatuses are widely used. An inkjet head (i.e., a printing head) employed in an inkjet printing apparatus is configured such that ink is supplied from an ink tank into manifolds and distributed to a plurality of pressure chambers defined in the inkjet head. By selectively applying pressure to the pressure chambers, ink is selectively ejected through the nozzles, which are defined corresponding to the pressure chambers, respectively. For selectively applying pressure to respective pressure chambers, an actuator unit composed of laminated sheets of piezoelectric ceramic is widely used.
An example of such an inkjet head is disclosed in U.S. Pat. No. 5,402,159, teachings of which are incorporated herein by reference. The above-described patent discloses an inkjet head which includes a piezoelectric actuator unit having laminated layers extending over a plurality of pressure chambers.
In the inkjet head of this type, it is desired that the pressure chambers are made smaller so that the plurality of the pressure chambers are arranged at the high density.
Further, in the inkjet head of the above type, electrodes (a common electrode and a driving electrode) are provided for each pressure chamber to sandwich one of more layers at a portion corresponding to each pressure chamber. By applying certain voltage to the electrodes, the piezoelectric layer(s) sandwiched between the electrodes deforms so that a pressure is applied to the ink in each pressure chamber. If the voltage potential difference between the common electrode and the driving electrode is made smaller, a driver for driving the piezoelectric actuator can be downsized, which may decrease the manufacturing cost of the inkjet head.
When downsizing of the inkjet head is considered, it should be noted that, if the pressure chambers are made too small and/or if the voltage potential difference described above is set too small, variation of the capacity of the pressure chambers may become insufficient and the sufficient amount of ink may not be ejected.